Like many things on this list, you might be able to purchase them onboard, but the objective for any cruise is to come prepared. It's no fun tracking down and overpaying for every little item you forget. After all, there are ice sculptures to gaze at. On the list of essentials to bring is your favorite insect repellent. You'll be pretty much bug-free in the open seas, but once you hit port, bugs can be gnarly. Most folks prefer their own brand of insect repellent, whether it's a highly powerful DEET-based product or a subtle-smelling remedy like Skin So Soft. There are creams and mousses, sprays, gels and moisturizing lotions to choose from. If you don't have a favorite, pick one that you don't mind wearing and pack it in a Ziploc bag, just to be sure it doesn't burst and leak all over your clothes.